Molecular beam epitaxial growth of CdTe and related II-VI materials on Si for the fabrication of infrared detectors and solar cells

CdTe/Si substrates with etch-pit densities similar to 5 x 10(4) - 2 x10(5) cm(-2) and x-ray diffraction full-width at half-maximum <60 arcsec over >60% of a 3 " substrate and <= 85 arcsec over the entire area are now available. Midwave and shortwave HgCdTe infrared detectors fabricated on these substrates have device characteristics as good as those of detectors fabricated on lattice-matched CdZnTe substrates. Also, minority carrier lifetimes of 100s of nanoseconds are measured for CdTe/Si and CdZnTe/Si, and both can be p-doped 10(17) cm(-3) and n-doped >10(20) cm(-3). Calculations suggest that the use of these materials should yield multijunction solar cells with efficiencies higher than those of the corresponding III-V multijunction cells at much lower cost, using rugged, large-area, inexpensive active Si substrates. The first CdZnTe/Si single-junction solar cells fabricated by EPIR displayed an electronic-charge times open-circuit voltage, qV(oc), within similar to 0.45 eV of the CdZnTe bandgap E-g, as good a result as that for the best III-V alloy single-junction cells, and confirmed the suitability of single-crystal CdZnTe/Si for the manufacture of high-efficiency solar cells.